1. Field of the Invention
The invention relates to a lighting device for an observation/image pickup apparatus, and more particularly to a lighting device for an observation/image pickup apparatus for observing or picking up an image of a surface of a specimen sample.
In particular, the present invention relates to a lighting device for an observation/image pickup apparatus for lighting a surface of a section to be observed (hereinafter referred to as "observed section") of a specimen sample by means of laterally projected light, deflected oblique light, vertically projected light, or light composed of laterally projected light and vertically projected light as required, or by means of any one of laterally projected light and vertically projected light selected as desired.
2. Discussion of the Background
An observation apparatus and an image pickup apparatus which have been conventionally used in the art are each generally constructed such that a lighting head or an image pickup head, having a light projecting means for illumination incorporated therein, is arranged opposite to a surface of an observed section of a specimen sample to light an observed section and/or obtain an image or enlarged image of the surface thereof. An observation apparatus allows the direct observation of the image thus obtained, whereas the image pickup apparatus is adapted to display the image on an image surface of a TV monitor, to thereby indirectly observe the observed section. In each of the observation apparatus and the image pickup apparatus, illumination of the surface of the observed section of the specimen sample with light is carried out by illuminating the surface of the observed section with only oblique light, which is directed obliquely from a side surface of the observed section (or light mainly consisting of so-called laterally projected light), or light illuminating the observed section with only parallel rays directed vertically from a flat surface of the observed section opposite to the surface of the observed section (or light mainly consisting of so-called vertically projected light).
The lighting techniques using light primarily consisting of laterally projected light or the lighting techniques using light primarily consisting of vertically projected light, fail to permit the roughness to be precisely observed, particularly when a plane surface section of the specimen sample has a relatively fine roughness formed thereon. In order to eliminate this problem, it could be considered to combine both lighting techniques. Unfortunately, such a combination can render the apparatus quite complex.